1908.] 



Use of Bracken as Litter. 



483. 



In another experiment bracken was tested against peat moss, 

 and the relative quantities of ammonia absorbed from a weak 

 solution were as follows : — 



Peat moss. Bracken. 



fe'- , ........ ioo ■ . - 25 



These figures, of course, cannot, lay claim to any absolute 

 value since the relative proportion of leaf and stem in the 

 bracken has so great an effect on its absorptive power ; they 

 show, however, that bracken is superior, weight for weight, to 

 straw. 



The power of retaining water and soluble substances varies 

 in the same way ; peat moss is best, bracken next, and straw 

 third; and again bracken owes its power largely to its small 

 leaves. These experiments were made with equal weights of 

 material ; if, however, an equal bulk be taken, bracken is 

 inferior to straw as an absorbent because it is so much lighter, 



The Composition of Bracken. — Although bracken has long 

 been used in agricultural practice very few analyses are recorded, 

 and these show, as would be expected; a certain amount of 

 variation because the composition of bracken depends to some 

 extent on the soil on which it grows and also on the time of 

 cutting. The young plant is richest in nitrogen and potash ; 

 before the leaf and stem die there is probably a transference 

 of some of the food material to the root just as takes place 

 in certain other plants, but a good deal is left behind and the 

 whole of this is secured if the bracken is cut in autumn as usual 

 and kept sheltered from excessive rain. Of course if it is left 

 out during the winter ,and not cut till after a great amount of 

 washing has taken place a loss of substance is likely to result. 



An important point about the composition of bracken is the 

 large amount of nitrogen present ; usually about 1 -3 per cent, 

 is found and even higher figures are recorded. Straw, on the 

 other hand, only contains about one-third of this, viz., -5 per 

 cent. The amount of potash shows considerable variation, 

 doubtless following the rather large variations in the small 

 amounts present in the light gravelly or sandy soils where, 

 bracken commonly grows. English samples usually show 

 about -i per cent. ; foreign samples are considerably higher, 

 The potash content of straw is also liable to variation, 

 but the average is probably somewhere between -6 and 1 per 



2 h 2 



